Localizer radio antenna array



Jan. 27, 1948. l D, J, K|TZE`R0W 2,434,934

LOCALIZER RADIO ANTENNA ARRAY Filed March l, 1945 6 Sheets-Sheet 2 INVENoR. paw/0 wwf/MW BYQMMQ/U,

Jan. 27, 1948. D.J.K1TzER'Ow 2,434,934

LOCALIVZER RADIO ANTENNA ARRAY Filed Mamh 1 1945 6 sheets-sheet s IN1/Enron. am@ ,z www v.II-m. 27, 1948. D, 1 KITZEROW 2,434,334

LOCALIZER RADIO ANTENNA ARRAY Filed March 1, 1945 6 Sheets-Sheet 4 Jan. 27, 14948. D. J. KlTzERow 2,434,934

LOCALIZER RADIO ANTENNA ARRAY A Filed March 1, 194s e sheets-sheet s Jan. 27, 1948. D. J; Krrzl-:Row

LOCALIZER RADIO ANTENNA ARRAY A 6 Sheets-Sheet 6 Filed March 1, 1945 Patented Jan. 27,1948

LOCALIZER RADIO ANTENNA ARRAY Donald J. Kitzerow, Dayton, Ohio. assigner to the United States of America, as represented by the Secretary of War Application March 1, 1945, Serial No. 580,456

6 Claims. (Cl. 343-109) (Granted under the act of March 3, 1883, as I amended April 30, 1928; 370 0. G. 757) The invention described herein may be manufactured and used by or for the Government for governmental purposes, without the payment to me of any royalty thereon.

The present invention relates to directional radio antennae and particularly of the type employed with directional signal airport landing facilities.

An object of the invention is to provide a localizer antenna array, having a iield pattern which is highly immune to atmospheric changes and stray reflections producing phenomena known as bends.

A further object is to provide means in such an array for sharply confining the field pattern of 'radiation for more accurate guidance of aire craft to a blind landing on an airports landing strip. y

A further object is to provide an antennae array which is symmetrical. directional and which will radiate a stronger signal in the on course direction than in all other directions.

A still further object is to provide directional elements on the ends of the array which will have very small coupling effect with the center radiators due to parasitic current.

A localizer ordinarily consists of ground radio transmitting equipment and antennae array which produce an equi-signal course of two different cycles in a vertical plane, the cardioidal field radiation patterns of which intersect the center line of the runway. An airplane approaching the. runway can, with suitable receiving equipment, follow the equi-signal course downwardly to a low approach on the runway during conditions ofpoor visibility and execute a safe landing.

Existing antennae arrays, however, produce field patterns of radiation which are susceptible to phenomena known as course bends which are caused by stray reections and course shifts due to precipitation. Under these conditions the pilot following the radiation eld intersections is thrown off the correct course and may not be brought to a safe landing on the runway. The points of intersection of such radiation nelds under the abnormal state mentioned may be of a wavy character or be oif to one side of the runway.

In order to minimize and very often eliminate such erratic field pattern conditions, the present invention employs preferably a pair of folded dipoles at opposite ends of a bank of loops or similar array. The dipoles serve as field compressors; that is, the radiated eld pattern is m'ade stronger at its longest and strongest sectors thereby sharpening the elds along the landing strip and immunizing them against distorting elements. In the preferred form of the invention, a bank of three circular loops are flanked on each side by a folded dipolearray, the driven dipoles, in turn, being flanked by a parasitic member on one side and a director-on the opposite side. To reduce stray reflection from the back course and to compress the field in the forward section of radiated field which would be rst encountered by ,the plane, abroad continuous empirical screen is used behind all three loops to let enough energy from the loops pass so as to maintain clearance in the back region and prevent nulls from occurring at degrees either side of the front course. Thus, a substantial reduction in sdeband patterns radiated in al1 directionsv except the front course is attained with a corresponding reduction in course bends.

Referring to the drawingsA wherein like numerals denote like parts,

Fig. 1 is a schematic diagram o'f the driven elements of the array to illustrate the circuit employed to connect the circular loop and the dipoles for transmitting the cycle and 150 cycle signals for producing the two fields defining the runway strip.

' Fig. 2 is a schematic top plan view of the array of loops and dipoles to illustrate forward oiisetting of the dipoles.

Fig. 3 is a schematic diagram of a circular loop of the array. illustrating the circular eld produced by such a loop. as distinguished from the unidirectional field of a dipole.

Fig. 4 is a plotted eld strength pattern obtained when using offset dipoles with-out reflectors and directors and using center loops as driven elements.

Fig. 5 is a plotted field pattern obtained when using only dipole driven elements.

Fig. 6 is a plotted eld pattern obtained when using driven center loop, side. offset dipoles with directorsand reilectors and an empirical screen rear reflector.

Fig. '7 is a top plan view illustrating schematically the relative locations of the array elements, without dipole offset.

Fig. 8 is a vertical elevation of the array of Fig. '1.

In the drawings. wherein the invention is shown for purposes of illustration, the array comprises a folded driven dipole lll on the left end flanked axially by a reflector ll and a director I2. Similarly on the right end another dipole I3 is flanked axially by a reliector I4 and a director I5. `Intermediately of these dipoles are arrayed a center loop I6 and end loops I1 and I8. To 'the rear of these antennae loops a continuous screen reflector I9 extends parallel to the plane of the three loops so as to act as a common reflector for all three. The effect of this common reflector I9 is to reduce the rear field of radiation, strengthen the fields against stray reflection by neighboring objects or vegetation, or moving vehicles.

The general arrangement of the array in its preferred form is shown in Fig. 1 to illustrate the circuit connections of the various elements. It will be noted that circular loops I6, I'I, I8 make up the central radiating array forming the main field patterns shown in Fig. 4. The feed lines to loops Il and I8 are connected at the top of the radio frequency bridge 32; likewise, a quarter wave shorted stub section is connected at the top of this bridge to divert a portion of the sideband energy to the dipoles. Shorting bar 29 provides a convenient adjustment for the proper amount of sideband energy diversion.

The entire array is fed two different cycle signals-one at 90 cycles through transmission line 30 and the other at 150 cycles through transmission line 3|. The resultant fields shown in Fig. 6 yield a. highly stabilized course.

Combining the dipole sideband pattern of Fig. with the three loop main group pattern results in the total pattern illustrated in Fig. 4. Adding directors and reflectors to the dipoles and the empirical screen to the three loop main group pattern results in the total patterns of Fig. 6. The

Ytotal patterns shown in Fig. 4. are derived from the three loop main group array by adding sideband energy to the front and back course up to within 30 degrees either side of front and back courses. From 30 degrees off either side of the front course to within 30 degrees of the back course, sideband energy is subtracted. however. 'I'his is because the positive lobes of Fig. 5 add to the main group pattern, while the negative lobes subtract energy. Thus, if reflecting objects causing bends are located o to the sides rather than within 30 degrees of front or back course the amount of energy directed towards the reflecting objects will be reduced with corresponding reduction in course bends.

A general description of the loops employed in this array is as follows:

The individual loops,y one of which is. shown schematically in Fig. 3 are made up generally of four radiating elements, 2|, 22, 23, 24, each of which is about two tenths of a Wave length long, mounted in the forxr of a square and supported at each comer with ceramic insulators on a central supporting cross-arm 25. Between two opposite corners of the square and inside of the supporting cross-arm is run a transposed balanced transmission line 26 called the cross-line. These two corners are called the fed corners. All four corners of the loop are loaded with capacitance 2l provided by the mechanical arrangement of the insulators and radiating elements to place the current maximum at or near the center of each element, and also to make the impedance of the loop at the input terminals real at the midband frequency. The magnitude of this impedance is controlled to a certain extent by the characteristic impedance of the cross-line 26. The loop, therefore, is provided with the proper impedance to match the transmission lines.

Due to the strength requirements of the insulators at the four corners, the insulators are made large and consequently too much capacitance results. To compensate for this excess capacitance and also to provide an impedance adjustment, an adjustable inductive loading stub 28 is connected across each of the two corners adjacent to the fed corners. These two adjustable inductive loading stubs are inserted in the cross-arms which support the two corners and the adjustable shorting wire is entirely enclosed so that it cannot be accidentally moved. 'I'he loop is fed at the center of the cross-line through a standard connector.

The eld pattern derived 'from a loop antenna is a circular field and consequently the phase will appear the same in azimuth regardless of the direction from which the loop is viewed.

Due to the difference of field current in a loop as compared to that of a dipole, a particular improvement of this localizer array is eected by offsetting the dipole side compressor arrays 10 to 15, ninety degrees forwardly of an imaginary center line running through the centers of the bank of loops I6, Il, I8. The dipoles are thereby phased so that the signals will be equally phased in the front and back course so that the full compression effect of the dipoles is exerted on the center array. y

Consideration of the manner of operation of a dipole antenna will illustrate the advantageous results of such an oiset arrangement.

If the phase of an Alford type loop 2I (such as the center loops here employed) is observed through an azimuthal angle of 360 degrees it will be observed that the phase remains constant, that is, the phase at 0 degrees and 180 degrees is the same. If, however, a dipole or folded dipole is observed azimuthally, the phase will be exactly opposite when viewed from opposite sides. That be 0 degrees but will be 180 degrees reversed when viewed from the rear course. This viewed phase reversal of the dipole, due to unidirectional current flow is overcome in the present invention by placing the folded dipoles degrees ahead of the centerline of the symmetrical loop array 2| to 24 and re-phasing the transmission lines to rephase thearray and compensate for the offset. When the dipolees are so offset 90 degrees, the azimuthal phaserelationship between the loops and dipoles will be correctly balanced and the viewed phase will be the same in both the back and front courses. This is true because when viewed from the back course the phase'of the dipoles viewed is degrees reversed from that viewed from the front course as aforesaid, but the signal emanating from the dipoles must travel an additional 180 degrees in distance in order to reach a similar offset position in the back course. In other words, since the dipole front offset is 90 degrees ahead of zero, the back oiset will be twice 90 degrees or 180 degrees. Thus, the 180 deg'ree reversal of the dipoles and the 180 degree phase lag due to longer distance traveled balance each other out and this results in the same phase relationship between dipoles and loops whethel` the array is viewed from the front or back course.

It is believed that from the foregoing description the operation of the invention will be sufiiciently clear to those familiar with the art, and while the-various components and circuits have been illustrated and described in their preferred embodiment, it is contemplated that changes in the details thereof may be made without departing from the spirit or scope of the invention as claimed.

Having thus described the invention, what is claimed is:

1. A directional localizer radio antenna array comprising main means for radiating directional adjacent cardioidal field pattern radiowaves and means for bilaterally confining and strengthening the long sectors of said patterns and comprising a foldedI dipole driven antenna array bilaterally and oppositely disposed in relation to said main radiating means, said driven dipoles being oppositely flanked by parasitic reflectors and directors.

2. A directional localizer radio antenna array comprising central means for radiating directional adjacent cardioidal field pattern radio waves and means for bilaterally confining and i strengthening the long sectors of said patterns and comprising a folded dipole driven antenna array bilaterally and oppositely disposed in relation to said central radiating means, said driven dipoles being oppostely fianked by parasitic reflectors and directors and an additional reflector disposed parallel to the plane of said main radiating means and to the rear thereof whereby the rear field pattern is reduced 'and the forward pattern is relatively increased in strength.

3. The method of propagating over an aircraft runway a pair of cardioidal radio wave field patterns of radiation having strong forward lineof-ight fields, relatively weaker rear line-cfflight fields, and a narrow common line-of-flight field therebetween, and comprising transmitting continuous signals from a multi-unit bank of loop radiators, simultaneously radiating from laterally spaced folded directional dipoles and reflecting forwardly the output of the array from an elongated reflector common to all of the multiunit bank of radiators, whereby stray reflection from the rear is eliminated, and the stronger sectors of the combined fields are concentrated in the area of the forward line-of-flight elds.

4. In a directional radio antenna, aligned loop radiator means for directing a concentrated pair of cardioidal pattern radio wave fields so'as to create a line-of-flight for blind-landing aircraft on a runway, folded dipole means for concenlit 6 trating said field bilaterally of said line-of-flight into a narrow sector along the runway, and refiector and director means for concentrating said fields more strongly in the forward line-of-flight section than in the rearward line-of-light section.

5. A directional radio antenna array for use with a localizer transmitter for guiding aircraft to a landing strip and comprising a row array of circular loop driven antennae, a pair of driven dipole antennae bilaterally flanking said circular loop array and being offset electrical degrees forward of the circular loop array and being provided with director and parasitic elements, and an empirical reflector screen spaced from and positioned behind the row of circular loops, whereby said dipoles laterally compress the transmitted nelds in phased relation and the empirical screen strengthens the forward field while reducing the rearward field.

6. An antenna array comprising three coplanar, equally spaced loop radiators, a pair of driven dipole radiators arranged bilaterally of said loop radiator and disposed in a plane that is parallel to the plane of said loop radiator and 90 electrical degrees forward thereof, a pair of parasitic directors positioned in front of said dipole radiators, a pair of parasitic reflectors positioned behind said dipole radiators, a screen reflector positioned behind said loop radiators and lying in a plane that is parallel to the plane of said loop radiator and rearward thereof, whereby a radiator pattern is provided having strong forward components, weak rearward components and minor lateral components.

DONALD J. KITZEROW.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS l Number Name Date 2,283,677 Kandoian May 19, 1942 2,289,899 Bond July 14, 1942 2,310,202 Alford Feb. 9, 1943 

